Android Hide Navigation Bar

根據 Android官方文件可在程式中隱藏Navigation Bar

MainActivity.kt

window.decorView.apply {
    systemUiVisibility = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION or View.SYSTEM_UI_FLAG_FULLSCREEN
}
 

但使用滑鼠點擊後，會顯示Navigation Bar，必須再呼叫此函式再將Navigation Bar隱藏起來即可。

何時觸發便是本篇所要談論的重點

我們先將之前Hide Navigation Bar的程式碼寫成函式：hideNavigationBar()。

MainActivity.kt

private fun hideNavigationBar() {
        window.decorView.apply {
            systemUiVisibility = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION or View.SYSTEM_UI_FLAG_FULLSCREEN
        }
    }
 

利用偵測螢幕大小的變化，當作觸發的時機。

MainActivity.kt

override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       setContentView(R.layout.activity_main)
       var relativeLayout = findViewById<RelativeLayout>(R.id.main_view)
       relativeLayout.addOnLayoutChangeListener(
              View.OnLayoutChangeListener { v, left, top, right, bottom,
               oldLeft, oldTop, oldRight, oldBottom ->

       })
   }
 

但由於OnLayoutChangeListener為Callback函式，處理UI變化時，不可在函式中處理。

所以我們必須創建一個Handler來呼叫hideNavigationBar函式

Source Code

MainActivity.kt

 class MainActivity : AppCompatActivity() {
    private var mUiHandler : UiHandler? = null
    private val HANDLER_HIDE_NAVIGATION_BAR = 1

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        mUiHandler = UiHandler(this)

        var relativeLayout = findViewById<RelativeLayout>(R.id.main_view)
        relativeLayout.addOnLayoutChangeListener(
            View.OnLayoutChangeListener { v, left, top, right, bottom,
                  oldLeft, oldTop, oldRight, oldBottom ->
                       if (bottom < oldBottom){ 
                          mUiHandler!!.sendEmptyMessageDelayed(
                              HANDLER_HIDE_NAVIGATION_BAR, 3000)
                       }
        })
        hideNavigationBar()
    }

    private fun hideNavigationBar() {
        window.decorView.apply {
            systemUiVisibility = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION or View.SYSTEM_UI_FLAG_FULLSCREEN
        }
    }

    private inner class UiHandler(obj: MainActivity) : Handler() {
        private val mObj: WeakReference<MainActivity> = WeakReference(obj)
        override fun handleMessage(msg: Message) {
            super.handleMessage(msg)
            when(msg.what) {
                HANDLER_HIDE_NAVIGATION_BAR -> {
                    hideNavigationBar()
                }
            }
        }
    }
}
  

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/main_view"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/test"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="Hello World!"
         />
</RelativeLayout>